Question

用配方法写出下列抛物线的对称轴和顶点坐标 y=﹣1/2x²+x-4

Answer 1

解：y=-(1/2)x²+x-4
=-(1/2)[x²-2x+1-1]-4
=-(1/2)[(x-1)²-1]-4
=-(1/2)(x-1)²+1/2-4
=-(1/2)(x-1)²-7/2
因此抛物线的对称轴为直线x=1,
顶点坐标为(1,-7/2).